Process for the manufacture of cellulose esters



Patented Aug. 6, 1935 PROCESS FOR THE MANUFACTURE OF CELLULOSE ESTERSAndreas Ruperti, Basel, Switzerland, assignor to the firm of Society ofChemical Industry in Basle, Basel, Switzerland No Drawing. ApplicationMay 26, 1930, Serial No. 455,967. In Switzerland June 1, 1929 Claims.(Cl. 8-20) The present invention relates to the manufacpronounced whenthe operation is conducted in ture of cellulose esters and to theproducts 015- complete absence of conditions which degrade tainedaccording to the new process. cellulose and in particular when noinjurious According to this invention cellulose esters are catalyst hasbeen used. Similarly very valuable made by the action of an organic acidanhydride are the bodies which may be obtained by im- 5 on the group ofcellulose derivatives consisting of pregnating, filling or saturating,dressing or the cellulose xanthogenates and the cellulose printing themost varied materials, particularly xanthic acid. The esters producedare free from the textile materials, with a solution of viscose, sulfur.(xanthate), and then treating the material thus 10 The acid anhydride,preferably anhydrides of prepared with the hot acid anhydride. In this10 aliphatic fatty acids, such as the anhydrides. of case'the celluloseester is formed in close union the acetic acid, propionic acid, butyricacid, etc., with the material and by further treating the latmay be usedas such or in a solvent and the reter by a dyeing operation portions ofthe fibre action may be facilitated by a catalyst. The which have beencovered or associated with the 1 process is a short one. There areobtained accellulose ester are immune to substantive dyecording to theconditions of operation various stuffs but are dyed by cellulose esterdyestuiis, highly esterified celluloses. Since the operation so thatmulticolor effects can be obtained. By is conducted in the absence ofagents capable of gentle treatment with acid anhydride the stagesplitting mineral acids and of catalysts having of esterification can bekept so low that the new a mineral acid reaction which degrade thecellumaterial has the advantage that it is insoluble 20 lose, thecellulose esters formed contain the celluin most of the commercialsolvents of acetate lose in non-degraded form. In esterifying solidsilk. However, by using energetic conditions cellulose xanthates orcellulose xanthic acid the complete esterification can be obtained. Byexternal form is retained, particularly if the acid varying theconditions of operation the lustre of anhydride is diluted with asolvent or used in the thread can be retained or aiiected in any de- 25moderate proportion, and if solvents are used sired manner. which do notdissolve the cellulose xanthogenates The following examples illustratethe invenand the cellulose esters produced therefrom. tion:-

The process finds application in many techni- Example 1 L cal operationsA cotton web is impregnated with a viscose 30 The process isparticularly interesting in that it made in known manner dried andtreated for 1h permits of wholly or in part esterifying formed hourswith acetic anh ydrlde, if desired in $9 lf g gff glif g ag ggf g 3212532 1; presence of xylene. During this treatment the 5 f th ten'l lforor the fibrous temperature is raised to 140 C. By this treatw re en Iono 6 ex ment the web acquires a durable dressing stable structure. Forexample, one may start from threads of a cellulose xanthate or acelluose xanggzigi g y whlch glves It Stlfi and thlck thic acid madefrom a viscose solution in the manner usual for making viscose silk butwith (0 use of a precipitating bath which, while caus- Viscose made by aknown process and in a 40 ing separation of the cellulose xanthate orcellucrude or purified condition is locally applied, for lose xanthicacid wholly or at least in part as instance by printing, to a web oryarn. The masuch, does not regenerate cellulose, or only in terial isdried and then treated with hot acetic part regenerates it; or it may befrom cellulose anhydride, the temperature being, for instance,

threads by treatment with alkali and carbon biat the boiling point. Theprinted places are re- 45 sulfide, while retaining the fibrous structureand served towards substantive dyestuffs but may be avo y dissolvingeffect during the producdyed vividly by means of acetate silk dyestuffs,tion. BY tr a c ad w th Organic acid the latter leaving the rest of thematerial unanhydride, for instance acetic anhydride, there dyed In thismanner various many colored Example 2 is obtained a thread whichpossesses the dyeing fects can be obtained. 50

properties of a cellulose acetate, being immune Example 3 towards d1rectdyestuffs; this 1s applicable as an effect thread and has considerablyenhanced A skem of cotton 1s immersed for 2 hours in physicalproperties, particularly in respect of wet an alcoholic potash solutionof 20 per cent. and dry tenacity. This tenacity is particularlystrength. Then centrlfuged or pressed and for several hours immersed incarbon bisulfide or subjected to the action of vapor of carbonbisulfide. cellulose xanthate acquiring a yellow color and becomingsoluble in water. After separating the excess of carbon bisulfide theskein is treated with hot acetic anhydride, for instance for 10 minutesto 1 hour at the boiling point of acetic anhydride, or for a longer timeat a lower temperature. The fibrous material thus obtained, thecomposition of which corresponds approximately with a cellulosediacetate, can be dyed vivid and deep tints by means of acetate sill;dyestuffs but is completely reserved towards substantive dyestufis.

In chloroform, glacial acetic acid and acetone the fibrous materialobtained is insoluble, while in pyridine and nitrobenzene swellingoccurs but no dissolution.

Example 4 Bleached wood pulp is converted in the usual manner intoviscose and the latter is spun. As precipitating bath there is used asolution of an allrali salt or an ammonium salt, acidified with aceticacid, or the bath may consist of methyl alcohol mixed with acetic acid.The precipitated thread, soluble in water, is treated with a solution or20 per cent. strength of acetic anhydride in toluene. The temperature isramd to the boiling point of the solution. There is obtained an estersills, which has the beautiful lustre, excellent wet tenacity and dyeingproperties of acetate sills. In chloroform, acetone, glacial aceticacid, pyridine and nitrobenzene the material obtained is insoluble.

. i Example 5 The xanthate thread obtained as described in Example 4':is treated with acetic anhydride at about 100 C., then centrifuged andwashed with water. There is thus obtained a lustreless, matte artificialsills. it before the material is washed, the still adhering aceticanhydride is separated by evaporation, the fibre obtained has the usualartificial sill; lustre.

Emmple 6 The skein is gradually converted into silk. The dyeingproperties of the material are analogous to those of acetate sills;substantive dyestuffs are reserved, acetate silk dyestufis are absorbed.In acetone, chloroform, glacial acetic acid the material is insoluble.

If instead of the solution of acetic anhydride a solution of 20 percent. strength of maleic anhydride in xylene is used, there is anincrease in weight of the material of about per cent. and a yellowishcolored product is obtained which is insoluble in chloroform, glacialacetic acid, acetone. py idine and nitrobenzene, and which has noaihnity for substantive dyestufls.

- What I claim is:-

1. Process for the manufacture of cellulose esters, characterized bytreating that group of cellulose derivatives which consists of thecellulose xanthogenates or of the cellulose xanthic acids with aliphaticcarboxylic acid anhydrides in the absence of organic acid halides.

. 2. Process for the manufacture of threadlike molded articles ofcellulose esters which is characterized by treating threadlihe moldedarticles consisting of that group of the cellulose derivatives whichconsists itself of the cellulose iranthogenates or of the cellulosexanthic acids, with allphatic carboxylic acid anhydrides in the absenceof organic acid halides.

3. Process for the manufacture of bodies of cellulose esters which ischaracterized by treating products consisting of that group of thecellulose derivatives which consists itself of the cellulosexanthogenates or of the cellulose xanthic "acids, with acetic acidanhydride in the absence of organic acid halides.

4. Process for the manufacture of cellulose esters characterized bytreating that group of the cellulose derivatives which consists of thecellu lose xanthogenates or of the cellulose xanthic acids, withaliphatic'carboxylic acid anhydrides in the absence of organic acidhalides, and in the presence of such diluents which are not capable ofdissolving the cellulose esters formed.

5. Process for the manufacture of threadlike molded articles ofcellulose esters, characterized by treating threadlilre molded articlesconsisting of that group oi the cellulose derivatives which consistsitself of the cellulose nanthogenates or of the cellulose :ranthicacids, with acetic acid anhydride in the absence oil organic acidhalides, and in the presence of such diluents whichare not capable ofdissolving the cellulose esters formed.

- ANDREAS RUPER'E'I.

